If I remember correctly, Nissan recommends a brake flush every two on our 2017 RS. This seems to me overkill and a way to increase profits for the dealer. What exactly does the dealer do? Drain and refill the brake fluid reserve canister. (Which is what I do every year.) Or do they go to every all four disk brakes and flush w/a vacuum pump or bleed the brakes? I will say even w/just doing the reserve canister, you will notice better braking performance. Ask what they'll do and if the price is reasonable, have the work performed if you're not comfortable doing yourself.